unnecessary blank in latex expression of multivariate polynomial

[dkrenn]

In the LaTeX representation of a multivariate polynomial is an unnecessary blank when variable is concatenated with a -, see

sage: R.<X,Y> = ZZ[]
sage: latex(X-Y)
X -  Y
sage: latex(X^2-X)
X^{2} -  X

It does not happen with +

sage: latex(X+Y)
X + Y

or with a constant

sage: latex(X-1) 
X - 1

In the univarate case the problem does not appear.

Note that this "wrong" output is no problem (i.e. a correct input for LaTeX)

CC: @EmmanuelCharpentier

Component: user interface

Keywords: latex, blank, multivariate polynomial

Work Issues: add additional regression test, formatting nitpicks

Author: André Apitzsch, Durgesh Agrawal

Branch: 86d9920

Reviewer: Debbie Matthews, Erik Bray, Emmanuel Charpentier

Issue created by migration from https://trac.sagemath.org/ticket/12908

[ppurka]

comment:1

Does this really need a fix? The latex output can be used in two ways:

1. Input to a latex document.
2. Display on the notebook with typeset.
   In both the cases, the output will be fine.

[a-andre]

Attachment: trac_12908.patch.gz

[a-andre]

comment:2

The attached patch removes the unnecessary blank.

But now we also have

sage: latex(-X^2-X)
-X^{2} - X

instead of

sage: latex(-X^2-X)
- X^{2} - X

Is this reasonable or should we find a solution to keep the blank between the leading variable and its sign ("-")?

[a-andre]

Author: André Apitzsch

[novoselt]

comment:3

No, it is not reasonable. As it was pointed out, the current output is correct and the only reason to "fix" is aesthetics. From this point of view, getting rid of a double space and swallowing a single one is not good - better to have more spaces then less.

[a-andre]

comment:4

Currently we have

sage: latex(-x^2-x)
-x^{2} - x
sage: R.<y> = ZZ[]  
sage: latex(-y^2-y)
-y^{2} - y

Notice, there is no blank in the leading term, if it's no multivariate polynomial.
So why do we need one if it's a multivariate polynomial?

IMO it should be consistent.